TN - When to use NX-PF**** and NX-PD****

There is a lot of confusion about when and which NX-PD and NX-PF power supply modules we should use. 

Summary/Issue Description

NX IO Modules can be installed on NX processors (NX1P2, NX102) and on NX-ECC (EtherCat) or NX-EIC (EIP) couplers.  The NX IO Units need 2 power supply line on the BUS. There is the power supply of the unit (internal electronic circuit) and the power supply for the IOs. 

On the NX-ECC and NX-EIC Couplers we Have the connections for the 2 power supplies. The "Unit Power Supply" power supply of the Units and the "IO Power Supply" Power supply of the IOs. In the case of NX Processors, there is only the power supply of the Units that is provided on the Bus Connector. So we must provide the power supply of the IOs on the IO Bus Externally. 

Explanation of each power supply needed

BUS Power supply of the units (NX-PD) 

The bus for the power supply of the units can support up to 10W and if the consumption of the NX IO modules exceeds this limit we must add a NX-PD1000 module. This module allows to start a new power supply Bus for the units. Sysmac studio automatically makes this calculation and will indicate when we exceed the 10W consumption for the units Power Supply. 

BUS Power Supply of the IO (NX-PF) 

The NX IO modules provide the power supply for the Sensor/Relay and other components used on the inputs and outputs. Depending on the models of Coupler and NX-PF there is a maximum current that can be supplied on the IO Bus (see data sheets for capacities). We have seen that on the couplers we already have the power the IO BUS. So if the total consumption of the components connected to the IO does not exceed the maximum capacity it is not necessary to add an NX-PF module. On the other hand if we exceed the maximum permitted current we will have to put an NX-PF Module to start a new IO power supply bus.

As mentioned earlier, NX processors do not provide power on the IO BUS and that is why we need to add a NX-PF module when we add NX-IO on these processors.

Conclusion 

In summary, on a NX Processor it is almost always necessary to put a NX-PF if we add NX-IO on the processor. Regarding the couplers we will add the NX-PF and NX-PD Modules as needed. One thing we must pay attention to is that the NX-PF and NX-PD Modules count in the maximum number of NX modules that we can put on the Couplers or on the NX Processors. 

The 2 types of modules can be used together as needed as in the following example.

Date/Revision History

First review 29/01/2025 V1.0

Author:

Jean Gervais, Senior Technical Support Engineer

References

All information can be found in the NX-ECC manual (W519) and the NX Processors manuals